The devices and techniques described herein were made in the performance of work under a NASA contract, and are subject to the provisions of Public Law 96-517 (35 U.S.C. xc2xa7202) in which the Contractor has elected to retain title.
This application relates to semiconductor radiation detectors, and in particular, to multi-quantum-well radiation detector arrays.
Semiconductor radiation detectors use optical absorption at optical transitions between two different energy levels to detect radiation by measuring the responses of the detectors caused by the optical absorption. Artificial multi-quantum-well structures have been used to construct various radiation detectors. The structures and properties of the multiple quantum wells can be selected to achieve desired detector performance with greater flexibility and freedom than extrinsically-doped semiconductor detectors. For example, an infrared quantum-well semiconductor detector usually includes a quantum-well structure formed of alternating active quantum well layers and barrier semiconductor layers. Such a quantum-well structure can have different energy bands each with multiple quantum states. An intraband transition between a ground state and an excited state in the same band (i.e., a conduction band or a valance band) can be used to detect infrared (xe2x80x9cIRxe2x80x9d) radiation by absorbing IR radiation at or near a selected resonance IR wavelength. The absorption of the radiation generates electric charge indicative of the amount of received radiation. The radiation-induced charge can then be converted into an electrical signal (e.g., a voltage or current) to be processed by signal processing circuitry.
The compositions of lattice-matched semiconductor is materials of the quantum well layers can be adjusted to cover a wide range of wavelengths for infrared detection and sensing. Quantum-well structures can achieve, among other advantages, high uniformity, a low noise-equivalent temperature difference, large format arrays, high radiation hardness, and low cost.
This application includes multi-quantum-well (MQW) detector devices that have a two-dimensional sensor array with spatially separated sensing regions responsive to different spectral bands. The sensor pixels in the sensor array have the same quantum-well construction which stacks together two or more different MQW structures respectively responsive to different spectral bands based on intrasubband transitions. Different pixels in different sensing regions, however, have different electrical configurations so that different sensing regions respectively detect radiation in their different, designated spectral bands. In addition, different pixels in different sensing regions also have different optical coupling designs so that the radiation of a designated wavelength for each sensing region is efficiently coupled into the active MQW structure in that pixel designed for detecting that designated wavelength.